Why was sexual immorality such a real temptation for the Corinthian believers?
Corinthian believers faced constant temptation because they lived surrounded by idolatrous worship and sexual immorality. Immoral priestesses were encountered daily, making fornication part of pagan worship, as with the golden calf. Paul therefore warned them to flee such practices rather than test Christ.
Les explains that the sexual immorality in view was not isolated sin but was part and parcel of going back into idolatrous worship, as in the golden calf episode. For the Corinthians, this was a real temptation because they lived in the midst of it and bumped up against immoral priestesses every day. Paul's instruction was a constant warning to flee from those things. He also warned against testing Christ, recalling Israel's sin and the poisonous serpents God sent, which got their attention; the brazen serpent on a pole provided healing when they were bitten.
Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand.